The present invention relates to an intake manifold, which is a component of an intake system of an automobile engine.
A conventional intake manifold of this type is disclosed in, for example, Japanese Laid-Open Patent Publications No. 11-141424 and No. 2005-61231.
Japanese Laid-Open Patent Publication No. 11-141424 describes an intake manifold for a horizontally-opposed engine. The intake manifold has a manifold body formed by joining an upper molded part and a lower molded part, each of which is formed of plastic, to each other through means such as vibration welding.
Japanese Laid-Open Patent Publication No. 2005-61231 describes a structure having a manifold body and a flow regulating valve, which is separate from a manifold body and incorporated in a downstream end portion of the manifold body. The flow regulating valve is employed to control the intake air amount of the engine.
As described in Japanese Laid-Open Patent Publication No. 11-141424, when a valve casing of a flow regulating valve is joined to an end portion of a curved downstream section of a manifold body through vibration welding, the downstream end may warp outward with respect to the curved portion. In the configuration described in Japanese Laid-Open Patent Publication No. 2005-61231, the flow regulating valve is inserted into and fixed to the manifold body of the intake manifold using bolts or adhesive. In this case, the manifold body is overlapped with the casing of the flow regulating valve so that the thicknesses are added up. This does not contribute to reduction in weight of the vehicle.
Accordingly, it is an objective of the present invention to provide an intake manifold that not only reduces the weight of a vehicle employing the intake manifold but also makes it unlikely that a manifold body warps at the time when a valve casing is welded to the manifold body.